Speaking as a former professional pistol instructor the thought of a pilot with a gun is frightening and probably increases the likelihood of loss of life. I have personally witnessed and heard of enough instances of 'professionals' letting a round off accidentally to know that it will be a matter of 'when' and not 'if'that a firearm is acccidentally (negligently) discharged inside an aircraft or on the ground. Despite what you read of in the papers and see on film, I also know that so-called 'safety slugs' will have no problem penetrating an aircraft skin. They are only 'safe' in that they don't penetrate a secondary target after passing through the first solid item they hit! A trained sky marshall uses a modified pistol and ammunition and spends many, many hours in practice- not a realistic prospect for a pilot.